Minor PHP Mail issue

I'm having a small issue with my php mail(); function. I believe it is because the "host_accept_relay = localhost" is commented out but when I uncomment it it gives me an error. Something to the effect that "host_accept_relay" is not an accepted setting by exim. Any ideas?

Regards,
Dennis M.

NOTE: I can send/receive mail without problems (via Squirrelmail/Horde) it's just sending with PHP's mail(); function does not work.